Owner's manual
4 Adjustments
50
Figure 4.39
ADJUST THE BOTTOM BRACKET
Three piece boom bracket: Adjustable
Typically the boom bracket contains four major pieces:
lockring, adjustable cup, spindle and xed cup. The lockring has
notched rings and the adjustable cup may have holes for a pin
spanner, or notches for a wrench. The xed cup will have wrench
ats, but no lockring. Cups and the spindle may be removed and
replaced separately. A set of round ball bearings are found in
each cup, typically eleven balls per side of 1/4 inch diameter.
This type of bracket may be cleaned, greased and adjusted.
Bearing Adjustment
The basic concept for bearing adjustments is to get the bearings
adjusted as loose as possible but without play. Start by purposely
beginning with play in the adjustment and then ghtening in
small increments unl play is gone. Note: Extended use may
cause the bearings, cups (or cones) to become worn and pied.
In this case, bearing adjustment will not be possible. If boom
bracket is correctly adjusted, but grinds when spun, cups and/or
cones are worn and should be replaced. Figure 4.39
❶ Loosen the locknut. Turn adjusng cone counter-clockwise
unl it hits the ball bearing, then turn back clockwise to
loosen 1/4 turn.
❷ Secure the locknut.
❸ Grab the end of the crankarms and rock it sideways to check
for play. If play is present, loosen locknut and turn adjusng
cone counter-clockwise slightly to ghten. Re-secure
locknut and check again.
❹ Repeat process of checking for play and re-ghtening cone a
slight amount unl no play is felt. Note: The one-piece crank
systems do not use a polished bearing system. There will be
some roughness to a correctly adjusted boom bracket.
Adjust as loose as possible but without play in the bearings.
Boom bracket shown with
crank arm removed
Lockring
Adjusng cup
Fixed cup
Bearings BearingsSpindle